It has long been recognized by golf club manufacturers that the shot making characteristics of a golf club may be adjusted by altering the position of the center of gravity of the club or, in other words, changing the heel-toe balance. Such an adjustment effectively serves to move the "sweet spot" toward or away from the heel or toe so as to bring the club into conformance with the swing tendencies of the golfer. In this way it is possible to insure more consistent and efficient transfer of energy from the golf club to the golf ball and, accordingly, the production of longer, straighter shots. Of course, by reducing and in some cases eliminating undesired slicing and hooking of the golf ball, an individual may reduce his or her golf score and increase his or her enjoyment of the game.
Many of the prior art proposals for weight adjustment and, accordingly, the customizing of a golf club to one's swing, have been unsatisfactory for a number of reasons. For example, U.S. Pat. Nos. 3,897,066 to Belmont; 4,180,269 to Thompson; and 4,655,458 to Lewandowski disclose club heads provided with passages or reservoirs for receiving weighty material such as lead powder, tungsten powder and/or liquid mercury. Unfortunately, upon adding any of these weighty materials in varying proportions to adjust the heel-toe balance and compensate for a particular swing, the overall swing weight of the golf club is also altered. This alteration in the swing weight often affects the speed and swing path of the golfer, many times negating the corrective effect that would otherwise be produced or actually compounding the problem. Further, it should be appreciated that the weighty materials, because they are liquid or powder, freely move within the reservoirs even in directions not parallel to the swing path. This creates a sloshing or mushy feel not conducive to providing the desired feedback to the golfer when striking the ball to allow the best playability.
Other golf clubs with adjustable weighting representative of the prior art are disclosed in U.S. Pat. Nos. 3,979,122 to Belmont; 4,340,230 to Churchward; 4,607,846 to Perkins; and 5,082,278 to Hsien. In these patents, a number of weights of differing mass are provided with one or more being positioned in cavities or threaded bores as required to provide the desired heel-toe balance. Once again, it should be appreciated that the total swing weight of the golf club is often altered when making adjustments with these systems and this factor alone can hinder the actual provision of any corrective effect resulting from weight redistribution. It should further be appreciated that unused weights must be stored until needed. As it may be a year or more between weight adjustments, the stored weights have a tendency to be misplaced, lost or forgotten thereby rendering this type of weight adjustment system essentially inoperative unless new replacement weights are purchased.
In addition to these shortcomings, prior art golf clubs with weight adjustment systems have failed to address a number of other issues of concern. Specifically, none known to this inventor that have been developed to date may be effectively utilized with irons of "perimeter weighting" design while fully maintaining the advantages of perimeter weighting. Further, none include weights that form an integral part of the club head structure and that have an overall mass equal to or greater than the golf ball so as to provide the most efficient transfer of energy resulting in longer hitting distances. Many of the prior art weight adjustment systems also serve to move club head weight well away from the central portion of the striking face adjacent the sweet spot, outwardly toward the heel and/or toe area. This has the disadvantageous effect of reducing the lift and distance provided to the ball being hit. Additionally, none effectively provide a full measure of adjustment to compensate for slicing and hooking in the manner of the present invention as described in the following.